The present invention relates to heat transfer devices and, more particularly, to the thermal performance and manufacturability of convoluted fin heat sinks.
Heat transfer devices, such as heat sinks and heat exchangers, are widely used for absorptive thermal protection. To achieve this, heat transfer devices are made of various types of corrugated fin material to allow energy transfer during passage of air and/or fluid through the device.
Compact, lightweight heat dissipators have become increasingly important with the constant trend of microprocessor and electronic device miniaturization. Traditionally, the highest performing heat sinks comprise thin folded fin structures for heat dissipation and a flat base, providing structural support for the assembly, as well as the interface to the electronic device. Such heat sinks are generally considered to have excellent performance, but at a very high cost. The high cost comes in part from the labor-intensive process of fixturing the fin and base assembly for precise alignment during the joining procedure. However, with electronic devices becoming ubiquitous, cost pressure virtually excludes traditional convoluted fin heat sinks from wide commercial use.
The long-used thin, lightweight convoluted fin for typical heat exchangers and dissipators is folded into a square wave shape with squared or rounded corners. In most cases, the structural base is a planar element with smooth surfaces. The interface between the fin and the base is a narrow contact area at the trough of the wave. When the fins are thin, the interface covers only a very narrow area. Furthermore, although a perfectly square wave shape will encourage higher contact with the base plate than a rounded or radiussed wave shape, perfectly squared corners at the trough of the fin material wave are unrealistic for the material used in fin forming.
It is known in the art that heat transfer can be improved in various applications by increasing the surface area of the fin material. The surface area of the fin material can be increased by either increasing the height of the fin material; increasing the number of fins per inch of the fin material; or increasing the width or flow length of the fluid along the fin. However, each of these improvements has tangible limits. For example, the part incorporating the fin material typically has a height and width limitation, which the fin material must adhere to in order to fit in the part. This is particularly the case with compact parts such as medical equipment, space applications, and computers, where increasing the size of the fin material and, therefore, the heat transfer device, is extremely undesirable. Additionally, increases in the height and/or width of the fin material does not create a directly proportional increase in the performance or efficiency of the heat transfer device. The other improvement technique, increasing the number of fins per inch, is theoretically sound, but realistically limited. The number of fins per inch is limited by the performance and ability of the corrugation means for corrugating the fin material.
It would be desirable, therefore, to have a fin heat sink with improved thermal performance and ease of assembly, without requiring a consequent increase in the surface area of the fin material.